Photographic exposure control apparatus

ABSTRACT

A PHOTOGRAPHIC EXPOSURE CONTROL MECHANSIM WHICH INCLUDES TWO EXPOSURE INFLUENCING BLADES. THE MOVEMENT OF THE BLADES IS GOVERNED BY A ELECTROMAGNETICALLY CONTROLLED LATCH. THE LATCH IS CAPABLE OF RELEASABLY RETAINING ONE BLADE AGAINST MOVEMENT WHILE PERMITTING MOVEMENT OF THE OTHER BLADE. A RESILIENT MEMBER EXTENDS FROM THE OTHER OF THE BLADES AND OPERATES DURING BLADE RETURN TO ADVANCE THE LATCH FROM ITS POSITION ASSOCIATED WITH BLADE RELEASE TO ITS BLADE RETAINING POSITION, WHERE IT IS CAPABLE OF HOLDING ONE BLADE AGAINST MOVEMENT. DURING EXPOSURE, THE OTHER OF THE BLADES IS RELEASED TO TERMINATE THE EXPOSURE. THEREAFTER, THE BLADES ARE RETURNED TO THEIR INITIAL POSITIONS WHERE THEY ARE RESET FOR FURTHER OPERATION.

NOV. 9, 1971 BELLOWS 3,618,501

PHOTOGRAPHIC EXPOSURE CONTROL APPARATUS Original Filed Dec. 5. 196'? N INVENTOR. LL KL 16:12am

73mm and 772m wrwl ATTORNEYS United States Patent Ofice" 3,618,501 Patented Nov. 9, 1971 3,618,501 PHOTOGRAPHIC EXPOSURE CONTROL APPARATUS Alfred H. Bellows, Cambridge, Mass., assignor to Polaroid Corporation, Cambridge, Mass. Continuation of application Ser. No. 688,176, Dec. 5, 1967. This application Nov. 19, 1969, Ser. No. 871,673

. Int. Cl. G03!) 9/26 US. CI. 95-60 9 Claims ABSTRACT OF THE DISCLOSURE A photographic exposure control mechanism which includes two exposure influencing blades. The movement of the blades is governed by an electromagnetically controlled latch. The latch is capable of releasably retaining one blade against movement while permitting movement of the other blade. A resilient member extends from the other of the blades and operates during blade return to advance the latch from its position associated with blade release to its blade retaining position, where it is capable of holding one blade against movement. During exposure, the other of the blades is released to terminate the exposure. Thereafter, the blades are returned to their initial positions where they are reset for further operation.

This is a continuation of application Ser. No. 688,176, filed Dec. 5, 1967.

SUMMARY OF THE INVENTION This invention contemplates use of photographic exposure control apparatus involving first and second blades biased for exposure influencing movement, electromagnetically controlled latch means for releasably holding the second blade against exposure producing movement, and a resilient member extending from the first blade for cooperation with the electromagnetically controlled latch means.

In the embodiment shown and described herein, the first blade is held in its first position by releasable means and the second blade is held in its first position by engagement between the resilient member and the electromagnetically controlled latch means. The electromagnetically controlled latch engages the second blade for holding it in its first position and the resilient member engages the latch to firmly hold it in its blade holding position.

Just prior to release of the releasable means to permit exposure influencing movement of the first blade, an electromagnetic device is energized to magnetically engage the latch to hold it in its blade holding position. The first blade is then released and moves to its second position. The resilient member moves out of engagement with the latch as the first blade moves out of its first position so that the latch is held in its blade holding position solely by the aforesaid magnetic engagement. After a timed inter-val the electromagnetic device is de-energized to release the latch, which in turn releases the second blade for movement to its second position.

The blades are reset to their respective first positions after each exposure producing operation. During the resetting operation, the second blade moves into its first position for engagement by the electromagnetically controlled latch means and the resilient member on the first blade moves the latch into engaging relationship with the second blade. The resilient member flexes as the first and second blades are moved to their first positions so that it continuously bears against the latch means to press the latch means firmly into its blade holding position.

The resilient member also serves to permit overtravel of the first and second blades beyond their first positions without damage to the apparatus if an excessive resetting force is applied to the blades.

It is an object of this invention to provide an improved exposure control apparatus.

It is also an object to provide a two-bladed electromagnetically controlled exposure control apparatus wherein a latch for releasably holding one blade against movement comprises an electromagnetic keeper for magnetic engagement by an energized electromagnetic device and wherein a resilient member is mounted upon the other blade for moving the latch into position for holding the one blade when the electromagnetic device is deenergized and retaining it in the blade holding position until the electromagnetic means is energized.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the apparatus of this invention prior to photographic exposure producing operation thereof;

FIG. 2 is a plan view showing the apparatus of FIG. 1 during exposure producing operation;

FIG. 3 is a plan view showing the apparatus of FIG. 1 after exposure producing operation; and

FIG. 4- is a view showing the apparatus of FIG. 1 during resetting operation.

DETAILED DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is shown in FIGS. 1 through 4. The apparatus of this embodiment includes means 10 forming an exposure aperture, first shutter blade means 12, second shutter blade means 14, resilient member 32, reset means 16, releasable retaining means 20 and electromagnetic retaining means 22.

First shutter blade means 12 includes shutter blade 13 pivotally mounted upon hub 18 and movable between a first position wherein it blocks the exposure aperture and a second position wherein it unblocks the exposure aperture. The shutter blade is continuously biased toward its second position by first drive spring 24. The first drive spring is attached to blade 13, at one end, by retainer 26, wound around hub 18 and attached to anchor 28 at the other end. First shutter blade means 12 also includes projection 30 extending therefrom for cooperation with retaining means 20. Blade means 12 further comprises an edge 33 (FIG. 2)' which forms an abutting surface for shutter blade means 14.

Second shutter blade means 14 includes shutter blade 15 pivotally mounted upon hub 18 and movable between a first position wherein it unblocks the exposure aperture aperture. The shutter blade is continuously biased toward its second position by second drive spring 34. Second drive spring 34 is attached, at one end, to retainer 35 on second shutter blade 15, wound about hub 18 and attached at its other end, to anchor 28. The second blade means also includes engageable means 36 extending therefrom for cooperation with electromechanical retaining means 22 and a light seal 40 mounted along the edge thereof adjacent edge 33 of blade means 12. Light seal 40 is arranged for abutting relationship with edge 33 of first blade means 12 to prevent light leakage between the first and second blade means.

In the embodiment shown and described, springs 24 and 34 form a biasing means for continuously urging the first and second shutter blade means for movement in the clockwise direction, toward their second positions. Stop 42 limits clockwise movement.

Resilient member 32 is mounted upon first blade means 12 and extends outwardly therefrom for cooperation with electromagnetic retaining means 22. In this embodiment, member 32 comprises a cantilever leaf spring fixedly attached, as by a weld, to blade 13 and extending angularly therefrom toward means 22.

Reset means 16 is pivotally mounted on hub 18 and biased for clockwise movement to a rest position, shown in FIGS. 1 through 3, by spring means 44. The reset means includes surface 43 to which a manual resetting force is applied and face 46 arranged to move into engagement with edge 48 of blade 13 when the resetting force is applied to surface 43.

Releasable retaining means 20 incorporates lever 50 pivotally mounted on support 52 and actuating means 55 arranged for cooperation with lever 50. Spring means 53 biases lever 50 for counterclockwise movement. Stop 120 is provided for limiting the counterclockwise movement. The lever includes an end surface 56, surface 58 adjacent surface 56 and end 60. Actuating means 55 includes button 54, shaft 64, collar 70 fixedly attached to shaft 64 and spring means 68. End 60 of lever '50- incorporates an opening, not shown, through which shaft 64 may pass. Spring 68 biases button 54 and shaft 64 in the direction of arrow 66. Movement of the button according to the bias of spring 68 is limited by engagement between collar 70 and surface 122 of button support 124.

Stop 120 and surface 122 are so located relative to each other that stop 120 halts counterclockwise movement of lever 50 in advance of contact between collar 70 and surface 122 so that a space, 72, is provided between the collar and end 60 of lever 50.

Electromagnetic retaining means 22 includes electrical timing circuit means 74, U-shaped core 76, coil 80 and latch means 82. The core defines two faces 78 and is mounted near the first position of second blade means 14. Coil 80 is wound around one leg of core 76 to provide an electromagnet. Latch means 82 comprises an armature for the electromagnet and is pivotally mounted upon post 86 for movement into and away from a position for magnetic engagement of the electromagnet.

Latch means 82 includes member 84 including a magnetizable portion in the form of a keeper 88 pivotally mounted thereon. Member 84 also includes extension 90 having cam surface 92 thereon and cam surface 94. To provide theaforesaid movement of latch means 82 into and away from a position for magnetic engagement by the electromagnet, member 84 is pivotally movable between a position wherein flat surface 96 of keeper 88 contacts surfaces 78 of core 76 and a position wherein flat surface 116 of member 84 abuts stop 98. Spring 100 is mounted adjacent extension 90 of member 84 for action against cam surface 92 to urge member 84 for action against cam surface 92 to urge member 84 toward the position against stop 98. Member 84 is movable to the position wherein the keeper abuts surface 78 of core 76 by cooperation between cam surface 94 and resilient member 32. Keeper 88 is pivotally mounted to member 84 by pin means 102 so that the keeper may move into a firm seating arrangement with both the faces 78 formed by U-shaped core.

The electrical timing means 74 may be of the type described in US. Pat. No. 3,241,471, which issued Mar. 22, 1966 to John P. Burgarella. The circuit includes a photoresponsive element, such as a cadmium sulfide photoconductor, arranged to receive light from a scene to be photographed and having a resistance which is functionally related to the level of scene brightness. The timing operation of the circuit is responsive to the resistance value of the photoresponsive element so as to increase or decrease the duration of each exposure interval in accordance with increase or decrease in the level of scene brightness, respectively. The circuit also includes coil 80 forming part of the electromagnet, as referred to above, and switches S and S Switch S comprises normally open resilient terminals 104 and 106 which are closable by movement of shaft 64 in the direction opposite that indicated by arrow 66. Switch S is held closed by projection 30 of blade means 12 when shutter blade means 12 and 14 are in their first positions. Switch S comprises rigid terminal 108 and resilient terminal 110'. The resilient terminal is biased away from terminal 108 so that switch S will open upon movement of first blade means 12 from its first position. The rigid terminal is adjustable to slightly vary the position at which switch S will open and thereby vary the amount of movement of blade means 12 which is required to open the switch. In operation, the circuit is completed when switch S is closed. Completion of the circuit is effective to energize coil of the electromagnet. When switch S is opened, the circuit operates to establish a timed interval, the duration of which is dependent upon the level of scene brightness. At termination of the interval, coil 80 of the electromagnet is de-energized.

For the purposes of discussion, the positions of the various elements of the apparatus as shown in FIG. 1

can be taken as the original position. The first and second shutter blade means are in their first positions, the opening blade means being held in its first position by releasable retaining means 20, and the closing blade means being held in its first position by engagement of resilient member 32 with latch means 82 while the latch means engages the second blade means, the latch means being magnetically engageable by the electromagnet when it is energized.

Operation of the apparatus will now be described. Referring to FIG. 1, button 54 is depressed manually against the action of spring 68. Initial movement of the button causes shaft 64 to engage terminal [104 of switch S to close the switch. Upon closure of switch S circuit 74 is completed and coil 80 is energized, as aforesaid.

Core 76 and keeper 88 form a complete magnetic circuit wherein the magnetic induction, when coil 80 is energized, is sufiicient to hold fiat surface 96 of the keeper against faces 78 of the core against the combined forces of second drive spring 34 and spring 100. Second shutter blade means 14 is thus held in its first position by latch means 82 of electromagnetic retaining means 22 independently of engagement between resilient member 32 and the latch means.

Further movement of button 54 causes collar 70 to engage end 60 of lever 50 and rotate the lever about support 52 against the bias of spring 53 to move end surface 56 away from projection 30 and release opening blade means 12 for movement to its second position under the influence of first drive spring 24. Movement of blade means 12 to its second position unblocks the exposure aperture to initiate an exposure interval. Projection 30 engages stop 42 to terminate movement of blade means 12 in its second position. This condition is seen in FIG. 2.

The initial aperture unblocking movement of blade means 12 moves resilient member 32 away from latch means 82 and causes projection 30 to move out of engagement with terminal 110 of switch 8;. Terminal 110 moves away from terminal 108 to open the switch. The opening of switch S initiates the timing operation of circuit means 74 to determine the duration of the exposure interval.

Upon completion of the timing operation, coil 80 is de-energized to magnetically release keeper 88 to permit movement of second blade means 14 to its second position to terminate the exposure interval, as shown in FIG. 3. When coil 80 is de-energized, member 84 of latch means 82 moves into abutting relationship with stop 98 due to the action of spring upon extension 90. Upon initial movement of member 84, it releases engageable means 36 to permit blade 15 to be driven to its second position under the influence of spring 34 to block the exposure aperture. In its second position, light seal 40 of second blade means 14 engages edge 33 of first blade means 12. After termination of the exposed interval, button 54 is released. The button and lever 50 are returned to their original positions by spring means 68 and 53 respectively.

The reset operation will now be described.

Referring to FIG. 4, manual pressure is applied to surface 43 of reset means 16 to rotate the reset mechanism about hub 18 against the bias of spring means 44. Face 46 of the reset means moves against edge 48 of the first blade means to move the first blade means toward and to its first position against the bias of its drive spring. Due to abutment of edge 33 of blade 13 with light seal means 40 on blade 15, the second blade means is also moved, against the bias of its drive spring, toward and to its first position. Light seal 40 prevents light leakage between the first and second blade means as they are being reset.

As the first and second shutter blade means are moved toward their first positions, engageable means 36 moves into the region near member 84 and, simultaneously, resilient means 17 contacts cam surfaces 94 of member 84. Continued resetting movement then moves member 84, against the bias of spring means 100, toward and to the position wherein surface 96 of keeper 88 abuts surfaces 78 of core 76. As surface 96 abuts surfaces 78, engeable means 36 moves into a position wherein it is engaged by member 84. As member 84 is being moved, resilient member 32 moves onto flat surface 116 of member 84.

Substantially simultaneously with movement of the keeper to the aforesaid position, projection 30 engages surface 58 of lever 50 to rotate the lever clockwise against the bias of spring 53 to permit the projection to pass the corner formed by surfaces 56 and 58. Lever 50 is then free to move counterclockwise and return to its position against stop 120, under the influence of spring 53. End surface 56 is thus positioned for engaging projection 30 and retaining, first shutter blade means 12 in its first, aperture blocking, position.

Resilient member 32 flexes an initial. amount as it drives keeper 88 into contact with core 76 and, as pressure continues to be applied to the reset mechanism after contact between the keeper and the core, the spring flexes additional amount-to permit overtravel of the reset mechanism and the fi rst and second shutter blades. The overtravel serves to insure that engageable means 36 is securely engaged by end surface 56 of lever 50. The arrangement by which overtravel is permitted also prevents damage to the mechanism when an excessive force is applied to the reset means.

When the reset means is released, it moves clockwise toward its rest position under the influence of spring means 44. The first and second drive springs then move the first and second shutter blade means clockwise until engageable means 36 is set against member 84 and projection 30 moves against surface 56. During this clockwise movement some of the fiexure in member 32 is relaxed but enough remains to continuously and firmly press latch means 82 into engagement with the core. Engagement of latch means 82 by resilient member 32 serves to hold the latch means in engagement with engageable means 36 of shutter blade means 14, prior to energization of coil 80, to hold the second blade means in its first position and to hold the keeper in position for magnetic engagement by the electromagnet when coil 80 is energized.

Movement of projection 30 into the position wherein it is engaged by lever 50 causes it to move terminal 108 of switch S into contact with terminal 110, thus closing switch S The apparatus is now returned to the position of FIG. 1 and set for a subsequent photographic exposure producing operation.

The terms clockwise, and counterclockwise and the like are used in the foregoing disclosure to describe movement of various elements as seen in FIGS. 1 through 4 and are not intended to be used in a limiting sense.

Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. Exposure control apparatus camera comprising:

(a) means forming an exposure aperture;

(b) first blade means movable from a first position wherein it blocks said aperture to a second position wherein unblocks said aperture for initiating a photographic exposure interval;

(c) second blade means movable from a first position wherein it blocks said aperture to a second position wherein it blocks said aperture for terminating said exposure interval;

(d) electromagnetic means;

(e) latch means, at least a portion of which is magnetizable, movably mounted adjacent said electromagnetic means, said latch means being movable into and away from a position wherein said magnetizable portion abuts said electromagnetic means, said magnetizable portion being magnetically engageable by said electromagnetic means when said electromagnetic means is energized and said magnetizable portion abuts said electromagnetic means;

(f) engageable means on said second blade means, said latch means releasably engaging said engageable means for holding said second blade means in its first position when said magnetizable portion of said latch means abuts said electromagnetic means;

(g) means for advancing said first and second blade means from their second positions toward and to their first positions between each exposure producing operation; and

(h) a resilient member extending from said first blade means for moving said latch means into abutment with said electromagnetic means when said first and second blade means are advanced to their first positions, said resilient member flexing as said first and second blades move to their first positions to press said latch means firmly against said electromagnetic means and hold said second blade means in its first position.

2. Exposure control apparatus according to claim 1 further comprising means for releasably retaining said first blade in its first position, said resilient member continuously engaging and holding said latch means firmly against said electromagnetic means while said first blade means is retained in its first position.

3. Exposure control apparatus according to claim 2 further comprising means operative prior to release of said first blade means for energizing said electromagnetic means so that said latch means is magnetically engaged by said electromagnetic means to hold said second blade means in its first position when said first blade is released.

4. Exposure control apparatus according to claim 3 further comprising means for de-energizing said electromagnetic means a timed interval after release of said first blade means to release said second blade means for movement to its second position.

5. Exposure control apparatus according to claim 4 further comprising means for biasing said latch means away from said position wherein said magnetizable portion abuts said electromagnetic means to facilitate rapid release of said second blade means upon de-energization of said electromagnetic means.

6. Exposure control apparatus according to claim 1 wherein:

(a) said electromagnetic means presents a number of coplanar faces against which said magnetizable portion of said latch means abuts; and

for photographic (b) said magnetizable portion of said latch means comprises a magnetizable keeper having a planar face for face-to-face abutment with said coplanar faces of said electromagnetic means, said keeper being movably mounted upon said latch means to facilitate said face-to-face abutment.

7. Exposure control apparatus according to claim 1 wherein said resilient member comprises a cantilever spring extending from said first blade means.

8. Exposure control apparatus according to claim 1 further comprising:

(a) means releasably retaining said first blade means in its first position;

(b) means continuously biasing said first and second blade means toward their respective second positions; and

(c) means responsive to releasing operation of said releasable retaining means for holding said second blade means in its first position while movement of said first blade means to its second position under the influence of said biasing means is permitted and for subsequently permitting movement of said closing blade means to its second position under the influence of said biasing means.

9. Exposure control apparatus for photographic camera comprising:

(a) means forming an exposure aperture;

(b) first blade means movable from a first position wherein it blocks said aperture to a second position wherein it unblocks said aperture for initiating a photographic exposure interval;

(c) second blade means movable from a first position wherein it unblocks said aperture to a second position wherein it blocks said aperture for terminating said exposure interval;

(d) electromagnetic means defining a number of coplanar faces;

(e) latch means movably mounted adjacent said electromagnetic means;

(f) magnetizable keeper means having a planar face, said latch means being movable into and away from a position wherein said planar face of said magnetizable keeper means abuts said coplanar faces of said electromagnetic means to facilitate magnetic engagement of said keeper means by said electromagnetic means when said electromagnetic means is energized, said keeper means being movably mounted upon said latch means to facilitate face-to-face abutment of said planar face thereof with said coplanar faces of said electromagnetic means;

(g) engageable means on said second blade means,

said latch means releasably engaging said engageable means for holding said second blade means in its first position when said planar face of said magnetizable means abuts said coplanar faces of said electromagnetic means;

(h) means for advancing said first and second blade means from their second positions toward and to their first positions between each exposure producing operation;

(i) a cantilever spring extending from said first blade means and engageable with said latch means for moving said planar face of said keeper means against said coplanar faces of said electromagnetic means when said first and second blade means are advanced to their first positions, said contilever spring flexing as said first and second blades move to their first positions to press said latch means firmly against said electromagnetic means and hold said second blade means in its first position; and

(1 means for releasably retaining said first blade in its first position, said cantilever spring continuously engaging said latch means and holding said planar face of said keeper means firmly against said coplanar faces of said electromagnetic means While said first blade means is retained in its first position.

References Cited UNITED STATES PATENTS 3,459,112 8/1969 Starp -60 SAMUEL S. MATTHEWS, Primary Examiner M. H. HAYES, Assistant Examiner 

